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From: David Sterba <dsterba@suse.cz>
To: Dennis Zhou <dennis@kernel.org>
Cc: David Sterba <dsterba@suse.com>, Chris Mason <clm@fb.com>,
	Josef Bacik <josef@toxicpanda.com>,
	Omar Sandoval <osandov@osandov.com>,
	kernel-team@fb.com, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 15/22] btrfs: limit max discard size for async discard
Date: Mon, 30 Dec 2019 19:00:37 +0100
Message-ID: <20191230180037.GZ3929@twin.jikos.cz> (raw)
In-Reply-To: <396e2d043068b620574892ebfc4b9f5c77b41618.1576195673.git.dennis@kernel.org>

On Fri, Dec 13, 2019 at 04:22:24PM -0800, Dennis Zhou wrote:
> Throttle the maximum size of a discard so that we can provide an upper
> bound for the rate of async discard. While the block layer is able to
> split discards into the appropriate sized discards, we want to be able
> to account more accurately the rate at which we are consuming ncq slots
> as well as limit the upper bound of work for a discard.
> 
> Signed-off-by: Dennis Zhou <dennis@kernel.org>
> Reviewed-by: Josef Bacik <josef@toxicpanda.com>
> ---
>  fs/btrfs/discard.h          |  5 ++++
>  fs/btrfs/free-space-cache.c | 48 +++++++++++++++++++++++++++----------
>  2 files changed, 41 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h
> index 3ed6855e24da..cb6ef0ab879d 100644
> --- a/fs/btrfs/discard.h
> +++ b/fs/btrfs/discard.h
> @@ -3,10 +3,15 @@
>  #ifndef BTRFS_DISCARD_H
>  #define BTRFS_DISCARD_H
>  
> +#include <linux/sizes.h>
> +
>  struct btrfs_fs_info;
>  struct btrfs_discard_ctl;
>  struct btrfs_block_group;
>  
> +/* Discard size limits. */
> +#define BTRFS_ASYNC_DISCARD_MAX_SIZE	(SZ_64M)
> +
>  /* Work operations. */
>  void btrfs_discard_cancel_work(struct btrfs_discard_ctl *discard_ctl,
>  			       struct btrfs_block_group *block_group);
> diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> index 57df34480b93..0dbcea6c59f9 100644
> --- a/fs/btrfs/free-space-cache.c
> +++ b/fs/btrfs/free-space-cache.c
> @@ -3466,19 +3466,40 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
>  		if (entry->offset >= end)
>  			goto out_unlock;
>  
> -		extent_start = entry->offset;
> -		extent_bytes = entry->bytes;
> -		extent_trim_state = entry->trim_state;
> -		start = max(start, extent_start);
> -		bytes = min(extent_start + extent_bytes, end) - start;
> -		if (bytes < minlen) {
> -			spin_unlock(&ctl->tree_lock);
> -			mutex_unlock(&ctl->cache_writeout_mutex);
> -			goto next;
> -		}
> +		if (async) {
> +			start = extent_start = entry->offset;
> +			bytes = extent_bytes = entry->bytes;

Please avoid chain initializations, I'll fix that unless there are more
updates to this patch.

> +			extent_trim_state = entry->trim_state;
> +			if (bytes < minlen) {
> +				spin_unlock(&ctl->tree_lock);
> +				mutex_unlock(&ctl->cache_writeout_mutex);
> +				goto next;
> +			}
> +			unlink_free_space(ctl, entry);
> +			if (bytes > BTRFS_ASYNC_DISCARD_MAX_SIZE) {
> +				bytes = extent_bytes =
> +					BTRFS_ASYNC_DISCARD_MAX_SIZE;
> +				entry->offset += BTRFS_ASYNC_DISCARD_MAX_SIZE;
> +				entry->bytes -= BTRFS_ASYNC_DISCARD_MAX_SIZE;
> +				link_free_space(ctl, entry);
> +			} else {
> +				kmem_cache_free(btrfs_free_space_cachep, entry);
> +			}
> +		} else {
> +			extent_start = entry->offset;
> +			extent_bytes = entry->bytes;
> +			extent_trim_state = entry->trim_state;
> +			start = max(start, extent_start);
> +			bytes = min(extent_start + extent_bytes, end) - start;
> +			if (bytes < minlen) {
> +				spin_unlock(&ctl->tree_lock);
> +				mutex_unlock(&ctl->cache_writeout_mutex);
> +				goto next;
> +			}
>  
> -		unlink_free_space(ctl, entry);
> -		kmem_cache_free(btrfs_free_space_cachep, entry);
> +			unlink_free_space(ctl, entry);
> +			kmem_cache_free(btrfs_free_space_cachep, entry);
> +		}
>  
>  		spin_unlock(&ctl->tree_lock);
>  		trim_entry.start = extent_start;
> @@ -3643,6 +3664,9 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
>  			goto next;
>  		}
>  
> +		if (async && bytes > BTRFS_ASYNC_DISCARD_MAX_SIZE)
> +			bytes = BTRFS_ASYNC_DISCARD_MAX_SIZE;
> +
>  		bitmap_clear_bits(ctl, entry, start, bytes);
>  		if (entry->bytes == 0)
>  			free_bitmap(ctl, entry);
> -- 
> 2.17.1

  reply index

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-14  0:22 [PATCH v6 00/22] btrfs: async discard support Dennis Zhou
2019-12-14  0:22 ` [PATCH 01/22] bitmap: genericize percpu bitmap region iterators Dennis Zhou
2019-12-14  0:22 ` [PATCH 02/22] btrfs: rename DISCARD opt to DISCARD_SYNC Dennis Zhou
2019-12-14  0:22 ` [PATCH 03/22] btrfs: keep track of which extents have been discarded Dennis Zhou
2019-12-14  0:22 ` [PATCH 04/22] btrfs: keep track of cleanliness of the bitmap Dennis Zhou
2019-12-14  0:22 ` [PATCH 05/22] btrfs: add the beginning of async discard, discard workqueue Dennis Zhou
2019-12-14  0:22 ` [PATCH 06/22] btrfs: handle empty block_group removal Dennis Zhou
2019-12-14  0:22 ` [PATCH 07/22] btrfs: discard one region at a time in async discard Dennis Zhou
2019-12-14  0:22 ` [PATCH 08/22] btrfs: add removal calls for sysfs debug/ Dennis Zhou
2019-12-18 11:45   ` Anand Jain
2019-12-14  0:22 ` [PATCH 09/22] btrfs: make UUID/debug have its own kobject Dennis Zhou
2019-12-18 11:45   ` Anand Jain
2019-12-14  0:22 ` [PATCH 10/22] btrfs: add discard sysfs directory Dennis Zhou
2019-12-18 11:45   ` Anand Jain
2019-12-14  0:22 ` [PATCH 11/22] btrfs: track discardable extents for async discard Dennis Zhou
2019-12-14  0:22 ` [PATCH 12/22] btrfs: keep track of discardable_bytes Dennis Zhou
2019-12-14  0:22 ` [PATCH 13/22] btrfs: calculate discard delay based on number of extents Dennis Zhou
2019-12-30 16:50   ` David Sterba
2020-01-02 16:45     ` Dennis Zhou
2019-12-14  0:22 ` [PATCH 14/22] btrfs: add bps discard rate limit Dennis Zhou
2019-12-30 17:58   ` David Sterba
2020-01-02 16:46     ` Dennis Zhou
2019-12-14  0:22 ` [PATCH 15/22] btrfs: limit max discard size for async discard Dennis Zhou
2019-12-30 18:00   ` David Sterba [this message]
2019-12-30 18:08   ` David Sterba
2020-01-02 16:48     ` Dennis Zhou
2019-12-14  0:22 ` [PATCH 16/22] btrfs: make max async discard size tunable Dennis Zhou
2019-12-30 18:05   ` David Sterba
2020-01-02 16:50     ` Dennis Zhou
2019-12-14  0:22 ` [PATCH 17/22] btrfs: have multiple discard lists Dennis Zhou
2019-12-14  0:22 ` [PATCH 18/22] btrfs: only keep track of data extents for async discard Dennis Zhou
2019-12-30 17:39   ` David Sterba
2020-01-02 16:55     ` Dennis Zhou
2019-12-14  0:22 ` [PATCH 19/22] btrfs: keep track of discard reuse stats Dennis Zhou
2019-12-30 17:33   ` David Sterba
2020-01-02 16:57     ` Dennis Zhou
2019-12-14  0:22 ` [PATCH 20/22] btrfs: add async discard header Dennis Zhou
2019-12-14  0:22 ` [PATCH 21/22] btrfs: increase the metadata allowance for the free_space_cache Dennis Zhou
2019-12-14  0:22 ` [PATCH 22/22] btrfs: make smaller extents more likely to go into bitmaps Dennis Zhou
2019-12-17 14:55 ` [PATCH v6 00/22] btrfs: async discard support David Sterba
2019-12-18  0:06   ` Dennis Zhou
2019-12-19  2:03     ` Dennis Zhou
2019-12-19 20:06       ` David Sterba
2019-12-19 21:22         ` Dennis Zhou
2019-12-19 20:34     ` David Sterba
2019-12-19 21:17       ` Dennis Zhou
2019-12-30 18:13 ` David Sterba
2019-12-30 18:49   ` Dennis Zhou
2020-01-02 13:22     ` David Sterba
  -- strict thread matches above, loose matches on Subject: below --
2019-12-09 19:45 [PATCH v5 " Dennis Zhou
2019-12-09 19:46 ` [PATCH 15/22] btrfs: limit max discard size for async discard Dennis Zhou
2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
2019-11-25 19:46 ` [PATCH 15/22] btrfs: limit max discard size for async discard Dennis Zhou
2019-11-20 21:50 [PATCH v3 00/22] btrfs: async discard support Dennis Zhou
2019-11-20 21:51 ` [PATCH 15/22] btrfs: limit max discard size for async discard Dennis Zhou
2019-10-23 22:52 [PATCH v2 00/22] btrfs: async discard support Dennis Zhou
2019-10-23 22:53 ` [PATCH 15/22] btrfs: limit max discard size for async discard Dennis Zhou

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